The invention relates to an analytic test unit for use in a test instrument for detecting an analyte in a bodily fluid, more particularly for blood sugar tests, comprising at least one test element, which is preferably provided in a cartridge and has a carrier film and a reagent layer, which is applied to a carrier side of the carrier film and to which the bodily fluid can be applied, wherein the light-transmissive carrier film can be positioned in the beam path of a photometric measuring unit for optically scanning the reagent layer. The invention furthermore relates to a test system for processing such test units.
By way of example, such analytic test units are used in portable blood sugar measuring instruments in order to enable the user to self-determine the blood sugar level in a largely automated measurement procedure. In the process, the reagent layer is wetted on the front side with a blood sample and measured photometrically on the rear side through the carrier film. The most common method for optical evaluation consists of shining light onto the film surface at an angle of between 30° and 60° and capturing the light diffusely reflected perpendicularly to the surface by means of a photodetector. Alternatively, the positions of illumination and detection can be interchanged. The purpose of these arrangements is to keep direct reflections at the surfaces of the test structure out of the detection beam path. Such reflections result in a very high signal level at the detector but have not interacted with the test chemicals and therefore do not contain any information in respect of the analyte, which changes the test chemicals optically. Moreover, even very small changes in the angle between light incidence or light emergence and mirroring surface bring about a large signal lift in the detected light which cannot be distinguished from the modulations of the reflectance due to the analyte. Such a beam path moreover requires a relatively large installation space, which is not available when test elements are integrated into a sample collector which should obtain the sample fluid by piercing the skin, at least if many of such integrated consumables should be stored in a confined space.
Proceeding from this, this disclosure is based on the object of further improving test units and systems and enabling optimum optical measured value capture with high measuring accuracy, particularly for compact hand-held instruments.